The present invention is directed to switching mode power supplies (SMPS). More particularly, embodiments of the invention provide circuits and methods for reducing standby power consumption of the SMPS. But it would be recognized that the invention has a much broader range of applicability.
Switching mode power supplies (SMPS) have the advantages of smaller size, higher efficiency and larger output power capability, and are widely applied in mobile phone chargers, notebook computer adapters and other fields. In recent years, green power supplies are emphasized, which require higher conversion efficiency and especially lower standby power consumption. This leads to the continuous reduction of switching frequency in light load or no load conditions of an SMPS, because lower switching frequency in light load or no load conditions can reduce switching loss of power transistor, thus increase power conversion efficiency and reduce system standby power.
Energy saving and environmental protection has become increasingly important. However commonly used in products such as adapter/chargers for shaver, cell/cordless phones, PDAs, MP3, and other portable apparatus, auxiliary power supplies continuously draw power as long as the product is plugged in, resulting in significant standby energy waste. Consumer electronic industry demands urgently for ultra low standby power supplies.
In view of the foregoing, there is a need for improved techniques for achieving low standby energy consumption switch mode power supplies.